1. Field of the Invention
This invention relates generally to the field of parts washing apparatus and particularly to a parts washing apparatus having a centrifugal filter to separate foreign waste elements from a cleaning solvent.
2. Background Art
Parts washers are widely used in industrial applications, and in particular, automotive service shops. The most familiar part washer can be found in almost any service station in the country. It is comprised of a sink with a spigot and a drain that sits upon a standard 45 gallon drum. The drum is partially filled with a parts washing solvent. The solvent is pumped from the drum, through the spigot, where it flows over the dirty part, into the sink""s drain, from which it falls back into the drum. In this manner, the solvent continuously flows over the dirty part while the operator washes the part in the sink.
The problem with these conventional parts washers is that the foreign material washed from the dirty part flows into the drum along with the solvent. In many applications, the foreign material will be comprised of metal shavings, dirt, sand, grit, and oil particulates. Since much of this debris will remain suspended in the solvent while the pump is running, the pump is continuously subjected to substances that will damage its internal seals. Much of the background art in this area has addressed this particular problem by placing a filter upstream of the pump to strain the foreign debris from the solvent before it reaches the pump. For instance, in U.S. Pat. No. 4,056,114 Boutillete), the pump is surrounded by a filter element. U.S. Pat. No. 3,890,988 (Lee) teaches a pump mounted at the top of a truncated cone that rests at the bottom of a solvent tank. The cone is made from a screen that is intended to filter the solvent before it reaches the inlet of the pump.
In U.S. Pat. No. 3,378,019 (Riolo et al.) the patent teaches a paper filter located below the drain. The solvent flows through the filter with only the assistance of gravity. U.S. Pat. No. 5,522,814 (Olson) also teaches a gravity filter comprising a compartment filled with waste cotton located below the drain. U.S. Pat. No. 2,675,012 (Scales) notes that these types of gravity filters are quickly obstructed by the gunk and will not filter the solvent. Accordingly, Scales teaches a complex set of superposed sludge settling trays of successively decreasing diameters. U.S. Pat. No. 2,085,075 (Delano) teaches a portable crankcase flusher and cleaner that introduces, extracts, and filters cleaning fluid from the crankcase of an automobile using a complicated reversible one-way valve.
Trapping the gunk and the solvent together until the solvent drains from the filter, however, insures that the gunk will retain a substantial amount of the solvent. This wet waste material will eventually condense into a thick, gummy, oily substance, commonly referred to in the art as xe2x80x9cgunk.xe2x80x9d
The second major effect of the foreign matter flowing freely into the drum along with the solvent is that, as the foreign material settles to the bottom of the drum it will accumulate and condense into gunk. This gunk layer will eventually foul, and probably damage, the pump. In any case, the solvent in the drum will eventually be so full of gunk and suspended matter that it will have to be replaced and the old solvent disposed of. In the age before hazardous waste laws, this problem was addressed in the art by using plastic drum liners that would capture the solvent, the foreign materials, and the gunk so that they could all be disposed of together - - - , probably ending up in a landfill (assuming the liner made it that far without being punctured). This disposable liner concept is taught in U.S. Pat. No. 3,890,988 (Lee). U.S. Pat. No. 3,552,814 (Olson); U.S. Pat. No. 4,056,114 (Boutilette).
Contrary to a suggestion in the Lee patent, it is no longer possible to remove the gunk and solvent together in a plastic liner to be disposed of in a landfill or, for the matter, in the dirt behind the service station. The solvents used in parts washers are now classified as hazardous waste materials and are heavily regulated by both state and federal law. There are severe civil and criminal penalties for the improper disposal of the waste materials associated with these parts washers. Similarly, it is no longer practical to clean the gunk from the parts washers because the gunk still has to be disposed of as hazardous waste.
Because of the hazardous waste laws, a huge industry has developed to service parts washers. The 1995 annual report from the largest of these service providers reports reclaiming more than 210 million gallons of contaminated fluids and discloses revenues in this area are in excess of $240 million dollars per year. Servicing the parts washers usually means removing the sink from the drum, capping the used drum off, and transporting the used solvent and gunk contained in the drum to a reprocessing plant. Evidencing the major concern that the industry has over hazardous waste liability, this service provider also advertises that it indemnifies the customer against liability hazardous waste spills that may occur while the solvent is being transported.
The various patents described above all address the same problemxe2x80x94dealing with the separation and removal of the gunk and preventing it from damaging the pump. They also all share a common problemxe2x80x94there is no way to stop the formation of the paste-like gunk that clogs filters, destroys pumps, and lessens the useful life of the solvent. The parts washing apparatus of the present invention significantly reduces these problems, and the hazardous waste problems associated with parts washers, by materially reducing the formation of the gunk by reducing the foreign waste material that reaches the solvent tank. This is done by employing a centrifugal filter assembly between the drain of the parts washing basin and the solvent storage tank. In this position, the centrifugal filter removes most of the foreign particulate matter from the solvent before the solvent is returned to its storage container. More importantly, however, is that the centrifugal filter removes the foreign waste material from the solvent before it can condense into the paste-like gunk at the bottom of the solvent storage tank. Instead, the centrifugal action of the filter squeezes the solvent from the foreign waste materials while the foreign waste material is still a small part of the solvent stream. A purified solvent is returned to the container, while the mostly-dried foreign matter is retained in the filter.
In the preferred form, a secondary xe2x80x9cscreenxe2x80x9d filter is used at the drain of the basin to capture larger foreign objects, including components that may fall off the part being washed. A tertiary filter is also preferably placed in communication with the solvent transfer means between the pump output and the solvent inlet to xe2x80x9cpolishxe2x80x9d the solvent by removing any fine particles or oils that may remain suspended in the solvent before it reaches the parts washing basin. These three filtering means enable the solvent to be recirculated almost indefinitely while remaining mostly free of gunk formation.
It is important to note that most of the foreign material is captured by the primary centrifugal filter, the secondary screen filter, and tertiary polishing filter, leaving a relatively clean solvent for reuse. In particular, these filters solve the problems associated with gunk accumulating at the bottom of a tank. The centrifugal action of the primary centrifugal filter spins most of the solvent out of the foreign material, leaving behind a body of foreign materials captured in the filter that is almost dry. Instead of capping off the whole solvent drum and sending it for reprocessing, the only material that need be sent to a hazardous waste facility are the disposable filters and their contents, which can easily be placed in a canister the size of a coffee can. This means that shipping and waste disposal fees will be significantly less, the danger of a hazardous waste spill will be considerably reduced, and the cost of replacing the solvent will almost be eliminated for most applications.
The parts washer assembly of the present invention can either be constructed as a complete unit or, a retrofit embodiment of the present invention can be installed in existing parts washers to incorporate the design benefits taught herein. In its preferred embodiment, as a complete parts washer, the apparatus is comprised of a parts washing basin that rests upon a drum acting as a solvent reservoir. The washing basin has a safety hood that is designed to drop and smother a fire if the fusible link holding it up is melted by a fire. The washing basin also has a solvent transfer means, (which usually comprises a spigot, but can also be a movable hose,) an access hatch and a drain. The drain is located in the center of the access hatch and the access hatch provides access to a centrifugal filter. The centrifugal filter assembly is mounted below the drain of the parts washing basin with a mounting bracket. The centrifugal filter assembly comprises a filter receptacle is rotatably mounted on the mounting bracket using a sealed bearing. Operatively connected to the filter receptacle is a motor that also is mounted on the mounting bracket. A pump hangs from the mounting bracket by a pump support and is submerged in solvent that partially fills the drum. To remove and replace the filter element located in the filter receptacle, the access hatch is removed from the parts washing basin, exposing the filter receptacle for easy access to the filter element. The filter element is removed from the filter receptacle and stored as hazardous waste for recycling. A replacement filter element is then draped inside the filter receptacle, with its upper edge folded over the upper edge of the filter receptacle, where it is secured to the filter receptacle with a securing means.
In a retrofit embodiment, the mounting bracket, together with the motor and the filter receptacle are removably mounted to the underside of the sink portion of an existing parts washer. The open portion of the filter receptacle should be positioned directly below the existing drain in the sink. The existing pump, or a new one, can be suspended from the mounting bracket using the pump support described below. However, if the original mounting of the existing pump does not get in the way of the retrofit assembly, it may be left in place. In either case, it is preferable that the pump and the centrifugal filter motor be wired in parallel to a single switch 170, so that both operate when the parts washer is turned on. Given the difficulty in retrofitting an access hatch in a existing steel parts washing basin, the hatch assembly will usually be omitted in a retrofit application. Therefore, it is important to mount the centrifugal filter assembly of the retrofit kit to the existing parts washing basin in a removable manner so that the centrifugal filter assembly may be lowered and the filter element in the filter receptacle replaced. Alternatively, most drains found in existing parts washing basins will be about four inches wide, which is usually enough room to reach in through the drain to remove and replace the filter element. A secondary and tertiary filter, as described herein, are also preferably included in the retrofit of an existing parts washer.